(CBS News) In separate interviews, the president and his challenger answer questions on topics of critical interest to America's voters -- including the economy and jobs, healthcare, national security and the federal budget. Steve Kroft interviews President Barack Obama, and Scott Pelley interviews Governor Mitt Romney.

Tonight, conversations with the candidates for president of the United States. We interviewed Barack Obama and Mitt Romney over the last few weeks and we asked about a wide variety of issues. The very first edition of 60 Minutes, in 1968, featured candidates Richard Nixon and Hubert Humphrey. Now, as we approach our 45th season, we hope you'll get a better picture of where today's candidates want to lead the country. Steve Kroft will talk with the president.

But we'll start with Gov. Romney. We asked Mr. Romney how his vision differs from the president's because recently Mr. Obama said this election is the clearest choice in a generation.

Gov. Mitt Romney: I think the president's right. I think this is a very clear choice for the American people as to what America's future will look like. The president's vision is one of a larger and larger government with trillion dollar deficits that promises everything to everyone. That's the course that he has laid out. His policy for the economy is more stimulus, more government spending. My course is very different than that. Mine says, "Make government smaller. Don't build these massive deficits that pass debt onto our kids, rebuild the foundation of America's strength with great homes, great schools, with entrepreneurship and innovation. Keep government as a-- if you will, facilitator of freedom in America. But don't have government take away the rights and the freedoms of the American people."

Scott Pelley: Ten years ago, when you were running for governor of Massachusetts, you were solidly pro-choice on abortion. Now you're against abortion, except in cases of rape, incest, or the health of the mother. When you were running for governor, you ridiculed the idea of signing a "no new taxes" pledge, and yet now you've signed one. Some people, Governor, have an uneasy feeling that you're not constant, that you say whatever you have to say in a particular moment.

The conversation continues online with the 2012 presidential candidates. Here's what you didn't see on the 60 Minutes broadcast.

Romney: Well they can look at my record. I understand that my opposition will do its very best to try and change, anyway they can, the narrative to fit their objectives. The president has certainly changed his view on a whole host of things. He was going to close Guantanamo. It's open. Military tribunals were going to be ended, now military tribunals continue. The president was opposed to same sex marriage, now he's in favor of same sex marriage. So I--

Pelley: But what about you?

Romney: So I--

Pelley: People wonder, "Does Romney believe the things that he says?" You say what to those people?

Romney: The principles I have are the principles I've had from the beginning of my political life. But have I learned? Have I found that some things I thought would be effective turned out not to be effective? Absolutely. If you don't learn from experience, you don't learn from your mistakes. Why, you know, you ought to be fired.

We spoke with the former governor of Massachusetts as he pitched a plan for a different nation; a government smaller than most Americans have ever seen, reform of Medicare and Social Security, a balanced budget and cuts in tax rates.

Pelley: What would the individual federal income tax rates be?

Romney: Well, they would be the current rates less 20 percent. So the top rate, for instance, would go from 35 to 28. Middle rates would come down by 20 percent as well. All the rates come down. But unless people think there's going to be a huge reduction in the taxes they owe, that's really not the case. Because we're also going to limit deductions and exemptions, particularly for people at the high end. Because I want to keep the current progressivity in the code. There should be no tax reduction for high income people. What I would like to do is to get a tax reduction for middle income families by eliminating the tax for middle income families on interest, dividends, and capital gains.

Pelley: The tax rate for everyone in your plan would go down.

Romney: That's right.

Pelley: But because you're going to limit exemptions and deductions, everybody's going to essentially be paying the same taxes.